Cathode active material comprising lithium manganese-based oxide and non-aqueous electrolyte secondary battery based upon the same

Abstract

Disclosed is a cathode active material including a lithium manganese-based oxide. The lithium manganese-based oxide has a spinel structure represented by Formula 1 below and high lithium ion diffusivity since (440) planes are predominantly formed in a crystal structure thereof. Li 1+x M y Mn 2-x-y O 4-z Q z   (1) In Formula 1, 0≦x≦0.3, 0≦y≦1, and 0≦z≦1, M includes at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti, and Bi, and Q includes at least one element selected from the group consisting of N, F, S, and Cl.

The invention claimed is: 
     
       1. A cathode active material comprising a complex comprising a lithium manganese oxide with a spinel structure represented by Formula 1 below,
 a first carbonaceous material having a particle diameter of 0.3 μm to 30 μm, and a second carbonaceous material having a particle diameter of 10 nm to 500 nm in a range smaller than the particle diameter of the first carbonaceous material, 
 wherein an intensity ratio of plane-(440)/plane (111) ((440)/(111)) measured by Rietveld refinement was 0.24 or greater, and 
 wherein the complex is formed by milling the spinel lithium manganese oxide with the first carbonaceous material and the second carbonaceous material:
   LiMn 2 O 4  (1) 
 
 wherein the lithium manganese oxide has a structure of secondary particles formed by aggregation of a plurality of primary particles, and 
 wherein the second carbonaceous material is disposed between primary particles of the lithium manganese oxide, and the first carbonaceous material is disposed at the external surface of the secondary particles of the lithium manganese oxide. 
 
     
     
       2. The cathode active material according to  claim 1 , wherein an intensity ratio of plane (440)/plane (111) ((440)/(111)) measured by Rietveld refinement was 0.25 or greater. 
     
     
       3. The cathode active material according to  claim 1 , wherein the second carbonaceous material is disposed between primary particles at a position between 0.3r to 1r from the center of a secondary particle with respect to the radius (r) of the secondary particle. 
     
     
       4. The cathode active material according to  claim 1 , wherein the content of the first carbonaceous material is in the range of 1 to 15 wt %, the content of the second carbonaceous material is in the range of 1 to 15 wt %, and a total weight of the first and second carbonaceous materials is in the range of 2 to 20 wt %, based on the total weight of the cathode active material, respectively. 
     
     
       5. The cathode active material according to  claim 1 , wherein the complex exhibits peak properties of graphite at 33° to 34° according to the XRD analysis using an Fe Ka target. 
     
     
       6. The cathode active material according to  claim 1 , wherein the first carbonaceous material comprises at least one selected from the group consisting of natural graphite and artificial graphite, and the second carbonaceous material comprises carbon black. 
     
     
       7. A cathode material comprising a cathode active material according to  claim 1 . 
     
     
       8. A cathode for a secondary battery prepared by coating the cathode material according to  claim 7  on a current collector. 
     
     
       9. A lithium secondary battery comprising the cathode for a secondary battery according to  claim 8 . 
     
     
       10. The lithium secondary battery according to  claim 9 , wherein the lithium secondary battery is used as a unit cell for battery modules that are power sources for devices. 
     
     
       11. The lithium secondary battery according to  claim 10 , wherein the medium and large-scale devices comprise electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, or power storage systems. 
     
     
       12. The cathode active material according to  claim 1 , wherein the milling is spex milling.